This invention relates to the field of aircraft flight instruments and their display arrangement and to display arrangements of this type which are convenient for use with electronic signal processing.
In order to control the flight of an aircraft, a pilot must know the aircraft's attitude with respect to the earth. Under favorable conditions, the pilot may determine this attitude to a degree by visual observation of the aircraft and the earth, however, under many conditions of flight, this visual observation is not possible.
In order to fly aircraft at night or under limited visibility conditions, and in order to know with a degree of precision the attitude of the aircraft with respect to the earth, it has become common practice to determine this attitude with the use of an attitude indicating instrument that is mounted in the aircraft cockpit. Indeed, an attitude indicator is often one of the principal flight control instruments and is usually mounted in a convenient and central cockpit location that is easily accessed by the pilot. Such attitude indicators in the past have taken the form of electromechanical instruments that are based on the pull of gravity, or more desirably, on a gyroscopic stabilized frame of reference. In more modern aircraft, at least the display portion of such instruments is often replaced with an electronic display employing, for example, a cathode ray tube, a light emitting diode matrix or a liquid crystal display assembly.
An undesirable feature of both the directly viewed electromechanical attitude indicator instrument and the more modern electronic displays of attitude information is their usual limitation to a field of view in the range of +30 or +40 degrees to -30 or -40 degrees. By way of this limitation, such displays are incapable of maintaining the artificial horizon in view of the pilot under many conditions of aircraft flight encountered in a high performance aircraft--such as the F-15 and F-16 that are currently used by the U.S. Air Force.
The absence of a horizon representation in the optical image of an aircraft display can also make interpretation of the display more difficult and/or more time consuming for a busy pilot or other aircraft crewmember. Particularly this effect is to be found under conditions of stress as may be induced by G forces, fatigue, hostile flight conditions, enemy activities, or other difficult environments encountered with a high performance aircraft. The display arrangement of the present invention improves upon this horizon absence condition and provides a number of additional advantages which will be apparent as the present disclosure ensues.
The patent art includes several examples of aircraft attitude indicating instruments which are in accordance with the above-described arrangement of such instruments. Included in this art is the patent of Francis Boyer, U.S. Pat. No. 4,882,845, which is concerned with a gyroscopic artificial horizon instrument of the self-contained gyroscope and display type.
Also included in this patent art is the patent of J. M. Reynaud, U.S. Pat. No. 4,878,054, which is concerned with a method and device for representing the horizon in an aircraft instrument and is also an example of an electronic display, including a cathode ray tube that is coupled to a computer-based attitude data processing arrangement.
Also included in this patent art is the U.S. Patent of Lennart Nordstrom, U.S. Pat. No. 4,513,509, which is concerned with an attitude direction indicator of the gyroscope-based type. The Nordstrom apparatus includes a spherical display element that is controlled by the gyroscope and read by the aircraft pilot through the use of an array of apex-inclusive pointer indicia appearing in a portion of the display.
Also included in this art is the patent of Ralph Hernandez Jr., U.S. Pat. No. 3,723,963, which is concerned with an aircraft gyrohorizon indicator with signal lamp positional attitude indicating means. The Hernandez Jr. indicator lamps provide the pilot with a quickly comprehendable indication of the aircraft's departure from straight and level flight by more than some reasonable limits of pitch and bank.
Although each of these prior patents presents aspects of the aircraft indicating instrument art which have been useful in improving the information available to a pilot, none of these patents provides an attitude display indication which is capable of the large angle and unique optical image patterns afforded by the present invention.